Hi,
I'm into beta testing and writing feedback to Google, Firefox and Ubuntu.
During my Firefox beta tests, I found an add-on called Thunderbird
Conversations
(at
https://addons.mozilla.org/pt-BR/thunderbird/addon/gmail-conversation-view/?src=userprofile
)
be given a big spotlight in the Mozilla Labs Google Group
(at https://groups.google.com/forum/#!topic/mozilla-labs/CZbSaSpnBxE ).
It can make complicated e-mail exchanges
(you know reply, subreply, an other subreply, subsubreply?)
look like a tree
(tc.png screenshot attached)
and if you don't like a part of it or all of it, you can write feedback
to Mozilla
(at https://getsatisfaction.com/mozilla_messaging/topics/new?topic ).
Since Mozilla made it, this may be the future of Thunderbird.